Power tools of all types comprise a body attached to which are handles by which an operator can support the tool. Vibrations are generated in the body during the operation of such tools which are transferred to the handles. It is desirable to minimize the amount of transfer.
A hammer drill can operate in one or more of the following modes of operation; hammer only mode, drill only mode and combined hammer and drill mode. EP1157788 discloses such a hammer. During the operation of such hammers, a considerable amount of vibration can be generated. The vibration is caused by the operation of the rotary drive mechanisms and/or the hammer mechanisms, depending on the mode of operation of the hammer drill, combined with the vibratory forces applied to and experienced by the cutting tool, such as a drill bit or chisel when it is being used on a work piece. These vibrations are transferred to the body of the hammer drill, which in turn are transferred to a rear handle being used by the operator to support the hammer drill. The transfer of vibration to the rear handle from the body, and subsequently to the operator's hand can not only be painful but can result in injury, particularly when the hammer drill is used over long periods of time. It is therefore desirable to minimise the amount of vibration transferred from the body to the rear handle.
One solution is to moveably mount the rear handle on the body of the hammer drill to allow relative movement between the two and to locate a vibration dampening mechanism between the body and the rear handle to minimise the amount of vibration transferred to the rear handle from the body.
GB2456805 describes such a vibration dampening mechanism for a hammer drill with reference to FIGS. 22 to 32 by which the amount of vibration transferred to the rear handle from the body is reduced. The rear handle 294 (using the same reference numbers as GB2456805) is connected via an upper mounting assembly 308, which enables the upper part of the handle 294 to slide relative to the upper part of the housing 290, and a lower mounting assembly 310, which enables a pivoting movement of the lower part of the handle relative to the lower part of the housing. Both the upper mounting assembly 308 and the lower mounting assembly 310 comprise vibration dampening mechanisms which reduce the amount of vibration transferred to the rear handle 294 from the housing 290.